#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cassert>

using namespace std;

const int MAXSTR=256;

int char2x(unsigned char c)
{
  if (c >= '0' && c <= '9') return (c - '0');
  if (c >= 'A' && c <= 'F') return (10 + (c - 'A'));
  if (c >= 'a' && c <= 'f') return (10 + (c - 'a'));
  return -1;
}

int main(int argc, char ** argv)
{
  int answer;
  unsigned short inval;
  unsigned char buf[MAXSTR];
  unsigned char uval;
  short sinval;
  char sval;
  unsigned char d1, d2;
  
  cout << "Requested Conversion?\n\t0: Exit\n\t1: unsigned dec->hex\n" <<
    "\t2: unsigned hex->dec\n\t3: signed dec->hex\n\t4: signed hex->dec\n";
  cin >> answer;
  while (answer) {
    switch (answer) {
    case 1:
      cout << "Enter decimal value in range (0..255): ";
      cin >> inval;
      assert (inval < 256);
      uval = (unsigned char)inval;
      printf("IN: %3d, OUT: 0x%2.2x\n", uval, uval);
      break;
    case 2:
      cout << "Enter hex value as two character hex digit sequence (00 to FF): ";
      cin >> buf;
      assert (char2x(buf[0]) >= 0 && char2x(buf[1]) >= 0);
      
      inval = char2x(buf[0]) * 16 + char2x(buf[1]);
      uval = (unsigned char)inval;
      printf("IN: 0x%2.2x (%s), OUT: %3d\n", uval, buf, uval);
      break;
    case 3:
      cout << "Enter decimal value in range (-128 .. 127): ";
      cin >> sinval;
      assert (sinval < 128 && sinval >= -128);
      sval = (char)sinval;
      d2 = sval & 0xf;
      d1 = (sval >> 4) & 0xf;
      printf("IN: %3d, OUT: 0x%1.1x%1.1x\n", sval, d1, d2);
      break;
    case 4:
      cout << "Enter hex value as two character hex digit sequence (00 to FF): ";
      cin >> buf;
      assert (char2x(buf[0]) >= 0 && char2x(buf[1]) >= 0);
      
      inval = char2x(buf[0]) * 16 + char2x(buf[1]);
      sval = (char)inval;
      d2 = sval & 0xf;
      d1 = (sval >> 4) & 0xf;
      printf("IN: 0x%1.1x%1.1x (%s), OUT: %3d\n", d1, d2, buf, sval);
      break;
    default:
      cout << "Unsupported operation, please enter integer 0 to 4\n";
    }
    cout << "Requested Conversion?\n\t0: Exit\n\t1: unsigned dec->hex\n" <<
      "\t2: unsigned hex->dec\n\t3: signed dec->hex\n\t4: signed hex->dec\n";
    cin >> answer;
  }
  
}